A feathered propeller has its blades moved to an extremely high pitch angle of approximately 90° so that they face perpendicular to the airstream and produce minimal aerodynamic drag. This may be done intentionally during a flight to decrease the drag on an airplane and, prevent windmilling of the propeller. As this function is often used in emergency conditions in flight, regular testing of propeller feather functions is performed. Such testing is used to exercise the feathering mechanisms of the propeller, in order to ensure that there are no dormant failures present within the feather activation system. This activation system may include any one of electronic, electrical, mechanical, and hydraulic features used to successfully feather the propeller.
The feather test is conducted manually by a pilot, at engine start and taxi-out of the aircraft. A push-button test switch is activated from the cockpit to command feathering of the propeller system. A successful feather test results in an audible drop in propeller speed which is detectable by the pilot. The feather test switch is then released to cancel the feather test operation.
There is a need to improve propeller feather testing functions.